It is difficult to readily determine whether an underground storage tank has been filled from a delivery vehicle. This is particularly true for sealed tanks wherein the delivery conduit is tightly fitted onto the inlet for the storage tank by a threaded coupling or the like.
A number of devices have been developed in the past to signal the operator when an underground storage tank is full. For example, U.S. Pat. No. 4,083,387 to Stieber shows a system for filling a storage tank in which the tank is provided with a sound transmitting device which is activated when the fluid reaches the level of the sound transmitting device. The system is relatively complicated including a microphone, amplifier and other electronic components. Some of these components are relatively fragile, and thus may not be well suited for the environment.
U.S. Pat. No. 4,176,694 to Dickerson shows an automatic shut-off liquid dispensing valve wherein audible means are provided to indicate that the tank is being filled. The audible means ceases when the tank is full. This audible means is in the nature of a gurgling sound.
U.S. Pat. No. 2,935,099 to Haynes relates to a signalling device for a filler pipe. Its whistle sounds until the liquid covers the inlet tube.
U.S. Pat. No. 3,548,779 to Green discloses a liquid signalling device whereby air exiting from the tank enters the opening of a tube and creates a whistling noise as it emerges from the opening. When the opening is covered, the sound stops.
All of the devices shown in these patents, with the exception of the Green device, are for use with pressurized delivery hoses. They are not adapted for use with gravity fed hoses. The Green device could be used with gravity fed hoses, but it appears that the underground tank would have to be specially modified.
An object of the invention is to provide a flow indicator for an underground storage tank suitable for use with gravity fed delivery hoses.
It is also an object of the invention to provide a device which does not require the discharge of polluting, vapour containing air from the device in order to make the audible sound.
It is also an object of the invention to provide a device of the type which does not require electronic components, and is relatively economical and rugged in construction.